Photographic stripping-film.



m. 670,| |8. I Patented Mar. l9. I901.

J. E. THORNTON &. C. F.v S. BOTHWELL. PHOTOGRAPH; STBlPPiNG FILM.

- (Apglication filed Mar. 6, 1900.)

(No Model.)

WITNESSES. INVENTORS- no: Nonms PETERS co. PHOTD-LIYHQ, wasnmumu. D c.

lUNrTnn STATES JOHN E. THORNTON AND CHARLES E. S. ROTHWELL, OF MANCHESTER,

ENGLAND.

PHOTOGRAPHIC STRlPPlNG-FILM.

SPECIFICATION forming part of Letters Patent No. 670,1 18, dated March 19, 1901.

Application filed March 6, 1900. Serial No. 7,541. (No specimens.)

To a. whom, it may concern..-

Be it known that we,JoHN EDWARD THORN- TON and CHARLES FREDERICK SEYMOUR Ro'rHwELL, subjects of the Queen of Great Britain, and residents of Manchester, in the county of Lancaster, England, have invented certain new and useful Improvements in Photographic Stripping-Films, of which the following is a specification.

The object of this invention is to provide a new or improved film for photographic purposes (of that class known as strippingfilms) which will have great advantages over those hitherto known, and improved methods of manufacturing such films.

Hitherto strippiugfilms have been produced by preparing a strong, thick, white, and comparatively opaque paper as a base upon which the sensitive emulsion has been spread to render it capable of being stripped or removed from the paper base in one of the following ways:

(a) The paper base has been coated with a thick coating of gelatin in one or several layers and the sensitive emulsion spread thereon in a thick layer. This gelatin coating being soluble at a lower temperature than the film of emulsion, it was placed in warm water to dissolve the soluble gelatin and permit of the removal of the paper base from the film. This process is troublesome and uncertain, involving a number of other operations requiring more dexterity and care than many photographers will exercise.

(b) The paper base has been coated with a covering of gum or other such substance, soluble in cold water or other liquids, to receive the sensitive emulsion; but such films are troublesome of manipulation and otherwise objectionable.

(c) The paper base has been coated or treated with a solution of lac or shellac, upon which the sensitive emulsion has been coated; but it was found that films so prepared would frequently refuse to strip or separate from the base as and when required, thereby rendering such films a failure.

(d) The paper base has been coated or treated with collodion or with rubber or with collodion and rubber to receive the sensitive film. These substances have allowed the film to be easily stripped or removed from the base, but frequently did not hold the film securely enough to the paper, the result being that the films often frilled during development and washing, and in some cases, owing to the rubber changing or hardening upon keeping, the films dropped off the paper before or during use.

(6) The paper base has also been coated or treated with one of the substances mentioned above to render the film capable of being stripped or removed, and the sensitive film has been strengthened or reinforced at some stage of the process by applying thereto a second film of insoluble gelatin, collodion, or the like. This has usually been done after the picture on the film has been passed through the operations of development, fixing, and washing. This process is objectionable, as it entails upon the photographer difficult manipulation which is not easily carried out.

In a stripping-film we find that it is of the utmost importance to secure success that the sensitive film should adhere perfectly to the paper base or backing during all the operations until finally dried and that then or at any time afterward it should be capable of being quickly and easily separated or stripped. Our invention accomplishes this to a degree of ease and perfection not hitherto attained.

Our invention consists, essentially, in preparing or coating a paper base with a compound or substance prepared by treating or dissolving the aluminium or zinc salts of fatty or resin acids (or a mixture of these salts) with a volatile light hydrocarbon solvent, such as benzol or coal-tar naphtha, and drying or solidifying same in a current of heated air and then upon this substance spreading a layer or coating of sensitive emulsion sufficiently thick to produce a strong film.

The drawing shows a perspective of the film.

As an example of a suitableformula for preparing the stripping medium E the following may be given; but the ingredients may be varied considerably and yet produce the required result: aluminium stearate, six per cent. aluminium resinate, two percent. aluminium palmitate, one per cent; aluminium oleate, two per cent; aluminium benzene, eighty-nine per cent; total, one hundred per cent. The zinc salts may replace the above aluminium salts. In carrying out the invention this prepared substance may be applied directto thepaper base A or it may be applied thereto after the paper has been first treated or coated with gelatin sizing or otherwise. The base A so prepared is then rolled or calendered by means of calendering-rollers until its'surface is perfectly smooth and free from grain.

The object of the smooth surface is to leave the film upon removal from .the paper with the highest possible degree of transparency and freedom from grain. If,however,a translucent instead of transparent film is desired, the rolling is omitted, whereupon the grained surface of the treated paper is reproduced upon the film.

' Upon the prepared calender-ed base of paper A is applied the sensitive emulsion, and

when this has been dried the film O is ready for use.

We prefer to build up our film by coating the treated paper A with gelatin mixed with chrome alum or other suitable hardening agent and then with gelatin emulsion, so as to obtain a film O of the requisite thickness and strength without the necessity of strengthening it by adding at some later stage of the process. WVe also prefer to coat the back of the paper with gelatin in order to prevent curling of the combined film in the developing and other solutions, or the paper may be run through a solution of gelatin before treatment.

It is advisable to add chrome-alum or other well-known hardening agent to the emulsion and also to the gelatin and for producing the strengthening-film for the purpose of making the films more or less insoluble when dried.

A film formed upon such a prepared paper base can be removed therefrom with the greatest ease by simply pulling the film and paper apart with the fingers, no heat nor solvents being necessary. Moreover, the film never comes ofi without being pulled and never fails to come ofi when desired.

Films can be manufactured in the way de scribed for various purposes, including rapid or slow gelatino-bromid emulsions for development, gelatino-chlorid emulsions for printing out or for development and also for negatives, kinematograph positives, lantern or window transparencies, and other purposes.

What we claim as our invention, and desire to protect by Letters Patent, is-

1. In aphotographic stripping-film the combination with an opaque paper base and a layer or film of sensitive emulsion, of a layer of a substance or compound composed of a salt of a fatty and resin acid dissolved and dried, interposed between the base, and the sensitive emulsion to render the latter capable of being stripped off and removed without extraneous aid substantially as described.

2. A photographic stripping-film comprising in its construction, a base of opaque paper, a stripping medium of a salt of a fatty and resin acid dissolved and dried, and a layer of sensitive emulsion, substantially as described. I

3. A photographic stripping-film comprising in its construction, a base of opaque paper, a stripping medium of a salt of a fatty and resin acid dissolved and dried, a layer of insoluble gelatin, and a layer of sensitive emulsion substantially as described.

4. In a photographic stripping-fil m the combination with an opaque paper base and a layer of sensitive emulsion, of a layer of a substance or compound composed of an aluminium salt of a fatty and resin acid, interposed between the base and the sensitive emulsion to enable the latter to be easily stripped and removed without extraneous aid substantially as described.

5. A photographic stripping-film comprising in its construction, an opaque paper base, a stripping medium applied thereto of an aluminium salt ofafatty and resin acid dissolved in a light hydrocarbon solvent and dried, and a layer of sensitive emulsion imposed thereon, substantially as described.

6. A photographic stripping-film comprising in its construction, an opaque paper base, a stripping medium applied thereto of an aluminiu 1n salt of a fatty and resin acid dissolved in a light hydrocarbon solvent and dried, a layer of insoluble gelatin, and a layer of sensitive emulsion, substantially as described.

In witness whereof we have hereunto signed our names in the presence of two subscribing witnesses.

J. E. THORNTON. O. F. S. ROTHWELL.

Witnesses:

J. OWDEN OBRIEN, HARRY BARNFATHER. 

